Performance evaluation of rice–fish integration system in rainfed medium land ecosystem

Abstract

This study was carried out for three successive years during 1999–2001 to evaluate growth and yield performance of fish, prawn and paddy under rice–fish integration system in rainfed medium land ecosystem. Irrespective of stocking density, faster growth rate was recorded for Catla catla followed by Cyprinus carpio, Cirrhinus mrigala, Labeo rohita and Macrobrachium rosenbergii. C. carpio and C. mrigala performed better growth rate against that of L. rohita probably due to the fact that being bottom dwellers, C. carpio and C. mrigala are more tolerant to fluctuation of oxygen concentration. Productivity of fish and prawn was, however, higher (p < 0.05) in refuges with 10-cm weir height plots, irrespective of stocking density, while overall yield performance was good at stocking density of 25,000 ha^–1. It was observed that, even with supplemental feeding, with increase in stocking density, biomass yield increased up to an optimum and then decreased. An average minimum and maximum yield of 906.6–1282.3 kg ha^–1 of fish and prawn has been achieved, which was much higher than the earlier recorded productivity in a season under rice-fish integration system. Highest grain yield was recorded at 15-cm weir height plot (3629 kg ha^–1), probably contributed by higher number of panicles per square meter (235.5) and number of filled grains per panicle (121.7). Percentage increase in rice yield under rice–fish integration system was 7.9–8.6% against control, where paddy was cultivated without integration of fish and prawn probably due to better aeration of water, greater tillering effect and additional supply of fertilizer in form of leftover feed and fish excreta. Irrespective of stocking density, the overall rice equivalent yield (REY) of the system was high (4.22–4.55 tons ha^–1) at 12.5-cm weir height plots-cum-refuge, without using any pesticide, herbicide, etc.

Introduction

Indian agriculture, on supply side, has been subjected to tremendous pressure to provide food security due to stagnation in net cultivated area and increased population, which needs optimum utilization of land resources, in situ water conservation, multiple use of stored water and, finally, integrated farming practice to match the food demand in the coming years. Out of 42 million ha of rice cultivated land in India, about 20 million ha is suitable for adoption of rainfed rice–fish integration system (Rao and Ram Singh, 1998). However, only 0.23 million ha is presently under rice-fish culture (Mohanty and Mishra, 2003), where a productivity of 200–800 kg ha^–1 offish has been obtained (Mukhopadhyay et al., 1991). Experience has proved the beneficial aspects of rice–fish integration system, which combines the principles of water conservation, soil improvement and biological control and plays an important role in sustainable production. Unfortunately, the carrying capacity of these suitable lands in India have not been utilized to the fullest extent. However, if these lands are brought under an integrated rice–fish system, it would help to compensate the economic losses in rice production brought about by natural calamities. This will also optimize the water and land use without bringing about environmental degradation. As paddy fields are complex ecosystems where primary producers and consumers at different levels compete with rice for material and energy, it decreases the overall productivity. However, fish culture in paddy fields can turn and recycle the available material and energy into fish production, accelerate the productivity of paddy fields and enhance the production potential of traditional farming practice (Caguan et al., 2000) with increased net income (Halwart, 1998).

Adoption and practice of rice–fish culture in India dates back almost 1500 years. The original system of integrated rice–fish farming, introduced to Southeast Asia from India, has flourished and developed from the low-input-based to intensive systems (Ali, 1990). However, despite great advances, several technical and production constraints are yet to be resolved such as yield gap between experimental and field models, inconvenience in pesticide application, and development of suitable design. It is also important to study the mechanism of rice–fish culture and the relationship among rice, fish and other factors such as soil, water, fertilization, etc. in the rice field. Although much works have been carried out on different aspects offish int egration system (Likangmin, 1988; Lightfoot et al., 1992; Huazhu, 1994; Fernando and Halwart, 2000; Kurup and Ranjeet, 2002), very little information are available on soil and water chemistry in relation to yield, impact of stocking density, design and management strategy to enhance unit yields. Keeping these in view, an attempt has been made to evaluate rice–fish integration system in rainfed medium land ecosystem with special reference to stocking density, growth performance of cultured species, system's rice equivalent yield and impact of weir height on system's overall performance.